n. an abnormal cell present in the blood and the blood-forming organs in one type of leukaemia (lymphoblastic leukaemia). It has a large nucleus with very scanty cytoplasm and is thought to be the precursor of the lymphocyte. —lymphoblastic adj.
According to the type of cells that predominate, leukaemia may be classi?ed as acute or chronic lymphoblastic leukaemia or myeloid leukaemia. Acute lymphoblastic leukaemia (ALL) is mostly a disease of childhood and is rare after the age of 25. Acute myeloid leukaemia is most common in children and young adults, but may occur at any age. Chronic lymphatic leukaemia occurs at any age between 35 and 80, most commonly in the 60s, and is twice as common in men as in women. Chronic myeloid leukaemia is rare before the age of 25, and most common between the ages of 30 and 65; men and women are equally affected. Around 2,500 patients with acute leukaemia are diagnosed in the United Kingdom, with a similar number annually diagnosed with chronic leukaemia.
Cause Both types of acute leukaemia seem to arise from a MUTATION in a single white cell. The genetically changed cell then goes through an uncontrolled succession of divisions resulting in many millions of abnormal white cells in the blood, bone marrow and other tissues. Possible causes are virus infection, chemical exposure, radiation and genetic background. The cause of chronic lymphocytic leukaemia is not known; the chronic myeloid version may have a genetic background.
Symptoms In acute cases the patient is pale due to anaemia, may have a purpuric rash due to lack of platelets, and may have enlarged lymphatic glands and spleen. The temperature is raised, and the condition may be mistaken for an acute infection (or may ?rst become apparent because the patient develops a severe infection due to a lack of normal white blood cells).
In the chronic type of the disease the onset is gradual, and the ?rst symptoms which occasion discomfort are either swelling of the abdomen and shortness of breath, due to painless enlargement of the spleen; or the enlargement of glands in the neck, armpits and elsewhere; or the pallor, palpitation, and other symptoms of anaemia which often accompany leukaemia. Occasional bleeding from the nose, stomach, gums or bowels may occur, and may be severe. Generally, there is a slight fever.
When the blood is examined microscopically, not only is there an enormous increase in the number of white cells, which may be multiplied 30- or 60-fold, but various immature forms are also found. In the lymphatic form of the disease, most white cells resemble lymphocytes, which, in healthy blood, are present only in small numbers. In the myeloid form, myelocytes, or large immature cells from the bone marrow, which are never present in healthy blood, appear in large numbers, and there may also be large numbers of immature, nucleated erythrocytes.
Treatment This varies according to the type of leukaemia and to the particular condition of the patient. Excellent results are being obtained in the control of ALL using blood transfusions, CHEMOTHERAPY, RADIOTHERAPY and bone-marrow TRANSPLANTATION. In the case of acute leukaemia, the drugs now being used include MERCAPTOPURINE, METHOTREXATE and CYCLOPHOSPHAMIDE. Blood transfusion and CORTICOSTEROIDS play an important part in controlling the condition during the period before a response to chemotherapy can be expected. Chemotherapy has almost completely replaced radiotherapy in the treatment of chronic leukaemia. For the myeloid form, BUSULFAN is the most widely used drug, replaced by hydroxyurea, mercaptopurine, or one of the nitrogen mustard (see NITROGEN MUSTARDS) derivatives in the later stages of the disease. For the lymphatic form, the drugs used are CHLORAMBUCIL, CYCLOPHOSPHAMIDE, and the nitrogen mustard derivatives.
Prognosis Although there is still no guaranteed cure, the outlook in both acute and chronic leukaemia has greatly improved – particularly for the acute form of the disease. Between 70 and 80 per cent of children with acute lymphoblastic leukaemia may be cured; between 20 and 50 per cent of those with acute myeloid leukaemia now have much-improved survival rates. Prognosis of patients with chronic lymphocytic leukaemia is often good, depending on early diagnosis.... leukaemia
Cancers are classi?ed according to the type of cell from which they are derived as well as the organ of origin. Hence cancers arising within the bronchi, often collectively referred to as ‘lung cancer’, include both adenocarcinomas, derived from epithelium (surface tissue), and carcinomas from glandular tissue. Sarcomas are cancers of connective tissue, including bone and cartilage. The behaviour of cancers and their response to therapy vary widely depending on this classi?cation as well as on numerous other factors such as how large the cancer is, how fast the cells grow and how well de?ned they are. It is entirely wrong to see cancer as a single disease entity with a universally poor prognosis. For example, fewer than one-half of women in whom breast cancer (see BREASTS, DISEASES OF) is discovered will die from the disease, and 75 per cent of children with lymphoblastic LEUKAEMIA can be cured.
Incidence In most western countries, cancer is the second most important cause of death after heart disease and accounts for 20–25 per cent of all deaths. In the United Kingdom in 2003, more than 154,000 people died of malignant disease. There is wide international variation in the most frequently encountered types of cancer, re?ecting the importance of environmental factors in the development of cancer. In the UK as well as the US, carcinoma of the BRONCHUS is the most common. Since it is usually inoperable at the time of diagnosis, it is even more strikingly the leading cause of cancer deaths. In women, breast cancer was for a long time the most common malignant disease, accounting for a quarter of all cancers, but ?gures for the late 1990s show that lung cancer now heads the incidence list – presumably the consequence of a rising incidence of smoking among young women. Other common sites are as follows: males – colon and rectum, prostate and bladder; females – colon and rectum, uterus, ovary and pancreas.
In 2003, of the more than 154,000 people in the UK who died of cancer, over 33,000 had the disease in their respiratory system, nearly 13,000 in the breast, over 5,800 in the stomach and more than 2,000 in the uterus or cervix, while over 4,000 people had leukaemia. The incidence of cancer varies with age; the older a person is, the more likely it is that he or she will develop the disease. The over-85s have an incidence about nine times greater than those in the 25–44 age group. There are also di?erences in incidence between sexes: for example, more men than women develop lung cancer, though the incidence in women is rising as the effects of smoking work through. The death rate from cancer is falling in people under 75 in the UK, a trend largely determined by the cancers which cause the most deaths: lung, breast, colorectal, stomach and prostate.
Causes In most cases the causes of cancer remain unknown, though a family history of cancer may be relevant. Rapid advances have, however, been made in the past two decades in understanding the di?erences between cancer cells and normal cells at the genetic level. It is now widely accepted that cancer results from acquired changes in the genetic make-up of a particular cell or group of cells which ultimately lead to a failure of the normal mechanisms regulating their growth. It appears that in most cases a cascade of changes is required for cells to behave in a truly malignant fashion; the critical changes affect speci?c key GENES, known as oncogenes, which are involved in growth regulation. (See APOPTOSIS.)
Since small genetic errors occur within cells at all times – most but not all of which are repaired – it follows that some cancers may develop as a result of an accumulation of random changes which cannot be attributed to environmental or other causes. The environmental factors known to cause cancer, such as radiation and chemicals (including tar from tobacco, asbestos, etc.), do so by increasing the overall rate of acquired genetic damage. Certain viral infections can induce speci?c cancers (e.g. HEPATITIS B VIRUS and HEPATOMA, EPSTEIN BARR VIRUS and LYMPHOMA) probably by inducing alterations in speci?c genes. HORMONES may also be a factor in the development of certain cancers such as those of the prostate and breast. Where there is a particular family tendency to certain types of cancer, it now appears that one or more of the critical genetic abnormalities required for development of that cancer may have been inherited. Where environmental factors such as tobacco smoking or asbestos are known to cause cancer, then health education and preventive measures can reduce the incidence of the relevant cancer. Cancer can also affect the white cells in the blood and is called LEUKAEMIA.
Treatment Many cancers can be cured by surgical removal if they are detected early, before there has been spread of signi?cant numbers of tumour cells to distant sites. Important within this group are breast, colon and skin cancer (melanoma). The probability of early detection of certain cancers can be increased by screening programmes in which (ideally) all people at particular risk of development of such cancers are examined at regular intervals. Routine screening for CERVICAL CANCER and breast cancer (see BREASTS, DISEASES OF) is currently practised in the UK. The e?ectiveness of screening people for cancer is, however, controversial. Apart from questions surrounding the reliability of screening tests, they undoubtedly create anxieties among the subjects being screened.
If complete surgical removal of the tumour is not possible because of its location or because spread from the primary site has occurred, an operation may nevertheless be helpful to relieve symptoms (e.g. pain) and to reduce the bulk of the tumour remaining to be dealt with by alternative means such as RADIOTHERAPY or CHEMOTHERAPY. In some cases radiotherapy is preferable to surgery and may be curative, for example, in the management of tumours of the larynx or of the uterine cervix. Certain tumours are highly sensitive to chemotherapy and may be cured by the use of chemotherapeutic drugs alone. These include testicular tumours, LEUKAEMIA, LYMPHOMA and a variety of tumours occurring in childhood. These tend to be rapidly growing tumours composed of primitive cells which are much more vulnerable to the toxic effects of the chemotherapeutic agents than the normal cells within the body.
Unfortunately neither radiotherapy nor currently available chemotherapy provides a curative option for the majority of common cancers if surgical excision is not feasible. New e?ective treatments in these conditions are urgently needed. Nevertheless the rapidly increasing knowledge of cancer biology will almost certainly lead to novel therapeutic approaches – including probably genetic techniques utilising the recent discoveries of oncogenes (genes that can cause cancer). Where cure is not possible, there often remains much that can be done for the cancer-sufferer in terms of control of unpleasant symptoms such as pain. Many of the most important recent advances in cancer care relate to such ‘palliative’ treatment, and include the establishment in the UK of palliative care hospices.
Families and patients can obtain valuable help and advice from Marie Curie Cancer Care, Cancer Relief Macmillan Fund, or the British Association of Cancer United Patients.
www.cancerbacup.org.uk
www.mariecurie.org.uk... cancer
Interferon alfa – previously termed leucocyte interferon or lymphoblastoid interferon – has some antitumour e?ect in some solid tumours and lymphomas. It is also used to treat HEPATITIS B and C (chronic variety). Various side-effects include suppression of MYELOBLAST production. Interferon beta – previously termed ?broblast interferon – is used (under restricted conditions in the UK) to treat patients with relapsing, remitting MULTIPLE SCLEROSIS (MS), and interferon beta-16 is licensed for use in patients with the secondary progressive type of this disorder. The use of interferon, which has a range of side-effects, should be recommended by a neurologist.... interferon
Side-effects include suppression of myelocytes in bone marrow, in?ammation of mucous membranes, and, rarely, PNEUMONITIS. It should be avoided whenever signi?cant renal impairment is present, while signi?cant pleural e?usion or ascites is also a contraindication. Blood counts should be carefully monitored whenever intrathecal methotrexate is given. Oral or parenteral folinic acid helps to prevent, or to speed recovery from, myelosuppression or mucositis.
Methotrexate is used in dermatology, where it may be indicated for cases of severe uncontrolled PSORIASIS unresponsive to conventional therapy; it may also be indicated for severe active RHEUMATOID ARTHRITIS. Because of its potentially severe haematological, pulmonary, gastrointestinal, and other toxicities it should be used only by specialists and appropriate renal and liver function tests carried out before and during treatment. It should be avoided in pregnancy, and conception should be avoided for at least six months after stopping, as should breast feeding. Concurrent administration of aspirin or other NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) reduces methotrexate excretion, increasing its toxicity, and should therefore be avoided whenever possible.... methotrexate
Exposure to certain chemicals (such as benzene and some anticancer drugs) or high levels of radiation may be a cause in some cases. Inherited factors may also play a part; there is increased incidence in people with certain genetic disorders (such as Fanconi’s anaemia) and chromosomal abnormalities (such as Down’s syndrome). People with blood disorders such as chronic myeloid leukaemia (see leukaemia, chronic myeloid) and primary polycythaemia are at increased risk, as their bone marrow is already abnormal.
The symptoms and signs of acute leukaemia include bleeding gums, easy bruising, headache, bone pain, enlarged lymph nodes, and symptoms of anaemia, such as tiredness, pallor, and breathlessness on exertion. There may also be repeated chest or throat infections. The diagnosis is based on a bone marrow biopsy. Treatment includes transfusions of blood and platelets, the use of anticancer drugs, and possibly radiotherapy. A bone marrow transplant may also be required. The outlook depends on the type of leukaemia and the age of the patient. Chemotherapy has increased success rates and 6 in 10 children with the disease can now be cured, although treatment is less likely to be completely successful in adults.... leukaemia, acute
Health Encyclopedia